Camera Projection - Nuke 101: Professional Compositing and Visual Effects - page 473

8. Connect Sphere1's output to another input of Scene1.
9. SelectScanlineRender1andpressthe1keytoviewit.Makesureyouareviewing
2D.
You just did a sky replacement. A pretty sophisticated one as well. There's still work to
do on it, though—as in, compositing.
Compositing Outside the ScanlineRender Node
At this point, you need better control over the kind of composite you are producing
between the buildings and the sky. At the moment, the ScanlineRender and Scene nodes
are doing the composite, but because Nuke is a compositing package it would be better to
do the composite using normal compositing tools.
Cloning nodes
To have two layers available for compositing outside the 3D scene, you need to split the
geometry into two sets and render each separately. You will need two Scanline-Render
nodes. However, with two ScanlineRender nodes, changing properties in one means you
havetochangepropertiesintheother.Thisisbecauseyouwantbothofthemtorenderthe
same kind of image.